Coordinate determining system



July 9, 1946. A. v. LoUGHRl-:N

COORDINATE DETERMINING SYSTEM Filed July 2, 1942 5 Sheets-Sheet lINVENTOR ARTHUR V, LOUGH REN July 9, 1946- A. v. LoUGHRl-:N

COORDINATE DETERMl-NING SYSTEM Filed July 2, 1942 3 Sheets-Sheet 2INVENTOR BY d 'ZNEY 4 3 DHOA July 9, 1946. A. v. LOUGHREN .2,403,729A4COORDINATE DETERMINENG SYSTEM 3 Sheets-Sheet 3 Filed July 2, 1942Patented July 9, 1946 COORDINATE DETERMINING SYSTEM Arthur V. Loughren,Great Neck, N. Y., assignor, by mesne assignments, to HazeltineResearch, Inc., Chicago, Ill., a corporation of Illinois ApplicationJuly 2, 1942, Serial No. 449,393

(Cl. Z50- 11) 13 Claims.

This invention relates in general to a system for determining thescanning coordinates of the position of an object within a predeterminedscanned space and, in particular, to such a system of the type in whichelectrical signals representative of the coordinates of the object arederived.

Although the invention is adapted for a wide range of applications, itis particularly useful in the eld of direction finding. One type ofdirection-finding system well known in the artcomprises asignal-reproducing device having an indicating area and means forproducing in the indicating area a signal pattern representing thelocation of an object within a predetermined space. A system of thistype forms the subject matter of copending application S`eral No.395,172, filed May 26, 1941, in the name of Arthur V. Loughren. It hasbeen proposed to provide a system of coordinates on the indicating areaof the signal-reproducing device of such an arrangement so that anobserver may obtain a visual indication of the coordinates of theposition of the object in space. While such an indication is suitable inmany instances, it will be appreciated that in many other instances sucha visual indication is not sufficient. For example, in gun-controllingsystems where accuracy is of paramount importance and where it ispreferred to provide automatic control equipment, a visual indication ofthe coordinates is not suitable for controlling the system.

It is an object of the present invention, therefore, to provide animproved system for determining a scanning coordinate of the position ofan object within a predetermined scanned space.

It is a further object of this invention to provide a system fordetermining a coordinate of the position of an object in space whichavoids one or more of the above-mentioned limitations of the prior artarrangements.

It is still another object of this invention to provide an improvedsystem for deriving an electrial signal representative of a scanningcoordinate of the position of an object within a predetermined scannedspace.

In accordance with the present invention, a system for determining thescanning coordinate in a given scanning direction of the position of anobject within a scanned space comprises means for effectively scanningthe space in a predetermined scanning pattern and for deriving a signalrepresenting the scanning coordinate in the aforesaid given direction ofthe position of the object within the scanned space. The system also hasmeans for deriving an electrical signal which represents any selectedscanning coordinate of the scanned space in the above-mentioneddirection and means responsive to the first-named signal for controllingthe last-mentioned means to derive an electrical signal which representsthe scanning coordinate in the aforesaid direction of the position ofthe object within the scanned space.

For a better understandingv of the present invention,` together withother and further objects thereof, reference is had to the followingdescription taken in connection with the vaccompanying drawings, and itsscope will bev pointed out in the appended claims.

Fig. 1 of the drawings is a circuit diagram, partly schematic, of asystem in accordance with the present invention for determining acoordinate of the position of an object within a predetermined space;FigJZ comprises a set of graphs Whichare used in explaining theoperation of a portion of the arrangement of Fig. 1; Fig. 3 is a circuitdiagram, partly schematic,rof a modicationcf a portion of thearrangement of Fig. 1;

while Fig. 4 isa circuit diagram, partly schematic,Y`

ofV a modication of the coordinate-determining system of the vpresentinvention.y

Referring now more particularly to the drawings, there is represented inFig. 1 asystem in accordance with the present invention for determininga scanning coordinate of the position of an object, such as an airplane,Within a predetermined scanned` space. This system comprises .means foreffectively scanning the space in a predetermined scanning pattern toderive a timemodulated signal representing vone scanningcoordinate ofthe position of the object within the space. While `any space-scanningmeans kmay be employed, it is preferred to utilize one of the typedisclosed in applicant's' above-identified c0- pending application. Thescanning means disclosed'in the arrangement of'Fig'. 1 is substantiallythe same as that employed in thelocating system disclosed in Fig. 2 ofthe above-identified cop'endingV application and corresponding elementsthereof -bear the same reference numerals. More specifically, thescanning meansv comprises aradiating system including means forradiating va sharply-concentrated beam and for causing the beam to scana predetermined space in a .predetermined scanning pattern. `To this endthere is provided an antenna system ID including a plurality of signalradiators ofthe dipole-antenna typ andra phase shifter and high-Yfrequency oscillator I l for applying a wave signal to the antennasystem I0 for directive radiation effectively inthe formof,ajsharply-concentrated beam. A line-scanning generator I3 is coupledto the high-frequency oscillator included in unit I I for varying therelative phase of the signals as applied to the signal radiators of theantenna system IG in a first dimension at a first predeterminedfrequency. A field-scanning generator I is also coupled to thehigh-frequency oscillator unit for varying the relative Iphase of thesignals as applied to the signal radiators of antenna Ill in a seconddimension at a second predetermined frequency. A timer I4 is coupled tothe linescanning generator I3 and field-scanning generator I5 forsynchronizing their operation. It will be understood that the units I0through I5 cooperate in a manner fully described in the aforementionedcopending application to vary the direction of transmission of thesharply-concentrated beam radiated by antenna system I0 in twodirections to scan a predetermined space with the beam.

When a reecting body, such as an airplane 20, is included within thespace scanned by the beam radiated by antenna system I0, atime-modulated signal representing the coordinate of the position of theobject within the scanned space in a particular direction may be derivedfrom energy reected from the object. Means are provided for receivingsuch reflected energy comprising a wave-signal receiver 2| having asubstantially nondirectional antenna system comprising two dipoleantennas 22, 23. Antenna 22 is preferably parallel to the dipoles ofantenna system I0, and antenna 23 is preferably at right angles theretoto provide a response to reflected waves having the polarization withwhich they were originally radiated or a polarization 90 degreesdisplaced from that radiated by antenna I0.

The system also includes signal-reproducing means responsive to thederived time-modulated signal 'for producing a visual indication of thecoordinates of the object Within the scanned space. This means comprisesa conventional cathode-ray type signal-reproducing device 24 having auorescent screen 25 as an indicating area. ning the indicating area 25with the electron beam of the reproducing device 24 in synchronism withthe scanning beam of antenna system III so that the position of anindicating spot on thei'luorescent screen 25 represents the direction ofthe object 20 from the antenna system I0. This scanning means comprisesline-scanning plates 25, 2l and field-scanning plates 28, 29 to whichare applied scanning voltages generated by line-scanning generator I3and held-scanning generator I5, respectively. The line-scanning voltageis applied by way of a compensating means included in unit 32 for apurpose to be described presently.

The signal output of receiver 2| is applied to the brilliancy-controlelectrode 3i] of tube 24 which comprises means responsive to thetimemodulated signal for producing on the indicating area a visualindication of the coordinates of the object within the scanned space.Cathode-ray tube 24 is so biased by a source I9 that it is cut off inthe absence of a received signal and suitable operating potentials aresupplied to the other electrodes of the tube in a manner Well understoodin the art.

Due to the fact that some time is required for the transmitted signal totravel from the antenna system I6 to the airplane 20 and back to theantenna system 22, 23, cathode-ray tube 24 tends to become excited byreceiver 2| with a time delay There arealso provided means for scanwhichmay be sufficient to give an inaccurate coordinate indication in theline-scanning direction, although it Will ordinarily be negligible inthe relatively low-frequency field-scanning direction. Therefore, it isdesirable to provide means for compensating for the time required forthe signal to travel from the radiating system to the receiving meansand this is accomplished by a compensating means comprising themodulator and detector unit 32. Unit 32 has one input circuit coupled tounit II whereby the signal output of the high-frequency oscillator isapplied to the modulator unit. To another input circuit of unit 32 thesignal output of receiver 2| is applied. A frequency-responsive networkand detector included in unit 32 are coupled in cascade to the outputcircuit of the modulator and are responsive to beat notes representingthe difference frequency of the signal inputs to the modulator. Thedetector unit preferably has a linear characteristic over the range ofsignal frequencies encountered in operation. The detector unit is soadjusted that the signal output thereof has such amplitude and polarityas to retard the line-scanning potential of tube 24 and cause it tocorrespond with the line-scanning potential of generator I3 at the timethe signal being received left the antenna I0.

In considering the operation of the system as thus far described, itwill be seen that antenna system Iii radiates a sharply-concentratedbeam which scans a predetermined space in a predetermined scanningpattern and that signals reflected from the airplane 2|) are picked upby the receiver 2|, thereby to derive a time-modulated signalrepresenting the scanning coordinate in one direction of the airplane 20within the scanned space. It will also be seen that the cathode-ray beamof tube 24 is caused to scan the indicating area 25 synchronously Withthe scanning of the predetermined space by the beam radiated from theantenna system I0. While tube 24 is normally biased beyond its cutoffpoint, it is operated above its cutoff point by the timemodulated signalapplied thereto from receiver 2| whereby a spot indication is providedon the fluorescent screen 25 representing the location of the airplanein the field scanned. Also, since the received signal is delayed in timewith reference to the signal output of the high-frequency oscillator ofunit b'y the time interval required for the signal to travel from theantenna I0 out to the airplane 2D and back to the receiver 2| and sincethe frequency of the oscillator has been altered during this time by theaction of the linescanning generator I3, the difference frequency ofthese two signals is a measure of this time. This difference frequencycauses an output voltage to be developed in the detector of unit 32which is applied to the deecting plates 2S, 21 and is effectivemomentarily to back up or retard the line-scanning potential of tube 24to cause it to correspond with the line-scanning potential generator I3had at the time the signal being received left the antenna I3. Thus, acompensation is effected and the spot indication on the area 25 affordsa visual indication of the coordinates of the airplane 2|) Within thescanned space. The system, as thus far described, is included in thelocating system disclosed in Fig. 2 of the above-identied copendingapplication and reference may be had thereto for a more completedescription of the operation of this portion of the arrangement underdiscussion.

In order to derive an electrical, as Well as a visual indication of ascanning coordinate of Ithe airplane within the scanned space, means areincluded in the arrangement of Fig. 1 for deriving an electrical signalrepresentative of any selected scanning coordinate of the scanningpattern in the above-mentioned direction, which means is controlled toderive an electrical signal that represents the desired coordinate ofthe airplane within the scanning pattern. This means, Which is indicatedgenerally as 35, includes a vacuum tube 38 having an input electrode 31and a control electrode 39 to which a suitable source of biasingpotential -C is coupled so as to bias the tube normally beyond cutoff.The output circuit of vacuum tube 38 includes a tuned circuit comprisinga condenser 4| and primary winding 42 of a transfromer 43, the circuitbeing resonant at the frequency of a reference Wave, to be describedpresently, applied to the input electrode 31. A peak rectier device 44is coupled through the transformer 43 to the output circuit of tube 38to derive a signal therefrom which is applied to a long time-constantcircuit comprising a condenser and load resistor 4B. An indicating meter45 is coupled to resistor 46. While load 45 is represented as aresistance, it will be understood that any circuit means adapted toutilize the derived signal may be used as a load for the rectier.

The reference Wave applied to input electrode 31 is related to thosescanning coordinates of the scanning pattern provided by indicatingdevice 24 that correspond to the coordinate of the airplane for which anelectrical indication is desired. Thus, in the arrangement underconsideration unit 35 derives an electrical signal representative of thecoordinate of the airplane 20 in the linescanning direction and, hence,the wave applied to input electrode 31 is related to the scanningcoordinates in the line-scanning direction. While a reference-Wavegenerator or oscillator may be utilized for supplying the reference Waveto electrode 31, it is found expedient to provide means for deriving thereference Wave directly from the line-scanning generator I3. To thisend, the

electrode 31 is coupled by way of conductor 38 and compensating unit 32with the line-scanning generator. This coupling is through unit 32 inorder that the reference signal may be compensated for the time requiredfor the time-modulated signa1 to reach the receiver 2|. modulated signaloutput of receiver 2| is applied through coupling condenser 40 tocontrol electrode 39, the latter comprising means responsive to thetime-modulated signal for controlling unit 35.

Considering now the operation of unit 35, it will be seen that, sincevacuum tube 38 is coupled to the line-scanning generator I3, a referenceWave of saw-tooth Wave form, which corresponds to the line-scanningvoltages applied to the high-fre quency osillator and to theline-scanning means of the reproducing device 2-4, is applied to theinput electrode 31. This wave is represented by curve A of Fig. 2 andcomprises a trace porsignal appears in its output circuit. However,

The timef trates such a received time-modulated signal h av-I ing anamplitude characteristic Which is varied Y with time and representingthe line-scanning coordinate of the object 2|) Within the scanned space,it being assumed that. the object 20 is sufcietly large to reect energyfrom the radiated beam to the receiver 2| in a plurality ofline-scanning operations.

pulses E which comprise electrical signals representing theline-scanning coordinate of the airplane 20 within space` and which arederived across vthe4 indicating meter '45 and load resistor 46 of unit35. Since the time-modulated signal B is delivered to units 32 and 35simultaneously, whereby the line-scanning voltage applied to inputelectrode 31 is momentarily backed up or compensated to take'intoaccount the time for the signal to travel from the antenna system IIJ tothe receiver 2|, the signal derived in unit 35 represents the true phaserelationship between the time-modulated signal and the scanning voltage.Thus, it Willbe seen that" unit 35 comprises means responsive totherelative phase of the reference wave and the time-modulated signal forderiving an electrical signal represent-r ative of the line-scanningcoordinate of the'airplane 28 Within the scanned space. Further, it willlbe seen that this means is responsive, to an instantaneous'amplitudecharacteristic of the reference Wave. Y

It has already been pointed out that the beam radiated by the antennasystem l0 is deliected in two directions and scans the predeterminedspace in ya two-dimensional scanning pattern. Therefore, thetime-modulated signal derived inthe scanning operation represents thescanning coordinatesof the position of the airplane 20 Within space inboth a line-scanning',direction and a iieldescanning direction. Unit 35has been shown" to be 'effective to derive an electrical signalrepresentative of the coordinateof'the airplane within space in aline-scanning direction. 'In order to obtain a similar electrical signalrepresentative of the coordinate of the airplane Within space intheeld-scanning direction, a field-scanning ysam'- pling circuit 41comprising 'Van arrangement sub'- stantiallyidentical to that of unit35, is provided. The refernce Wave in this instance, howevenvis suppliedrdirectly from the held-scanning 'generator l5 to unit 41 for the reasonthat the delay of the signal in traveling from the antenna system I0 tothe signal receiver 2| by way of reilection from the body2ll is assumedto have a negligible effect in the field-scanning direction. Thetime-modulated signal received by receiver 2| is also applied to unit41and, in a manner-already described in 'connection with unit 35, ranelectrical signal is derived in unit lllwhiclis representative `of thecoordinate of the airplane 28 Within space Yin the field-scanning 'Ydirection. Hence, it may be seen that, inthe arrangement of Fig. 1, thereproducing device'r24 aiiords a vis,- ual indication of the coordinateof an object in space with respect to boththe line and iield-scanningdirections and units'35 and 41, respectively,

produce electrical signals representative of the coordinates of theobject within space in linescanning and eld-scanning directions.

By projecting the curve B upon curveA, there are determined the It willbe appreciated that, when a plurality of airplanes is included withinthe space scanned by the beam from antenna system l0, the derivedtime-modulated signal represents the scanning coordinates of theposition of each airplane within the scanned space. Under such operatingconditions, several indications, represented by the spots on theuorescent screen 25 of Fig- 3, are produced, each of which representsvisually the coordinates of one of the airplanes within the scannedspace. The line-scanning sampling circuit and eld-scanning samplingcircuit may also derive a plurality of electrical signals individuallyrepresenting the coordinates of each of the airplanes within the scannedspace. To facilitate the operation of the system of this invention undersuch operating conditions, and to derive electrical signalsrepresentative of the coordinates of a predetermined one of theairplanes Within the space, the system may be modified as indicated inFig. 3 to include means for selectively applying only a portion of thetime-modulated signal to the sampling circuits. Referring now moreparticularly to Fig. 3, there is disclosed an arrangement of thesignal-reproducing device 24, line-scanning sampling circuit 35,field-scanning sampling circuit 41, and a means 48 for applying aselected portion of the time-modulated signal to the sampling circuits.'I'he arrangement of Fig. 3 may be substituted in the arrangement ofFig. l by connecting the terminals A, B, C, D, and E of Fig. 3 to thecorrespondingly identified terminals of Fig. l. Unit 48 comprises aphotocell 49 around which there is a shield 50 having a relativelynarrow aperture 5I. The output circuit of photocell 49 is connectedthrough an amplier 52 and a diierentiating circuit 53 to theline-scanning sampling circuit 35 and the eldscanning sampling circuit41.

Considering now the operation of the arrangement of Fig. 3, it will beunderstood that units 24, 35 and 41 operate in precisely the same mannerin response to an applied time-modulated signal as described inconnection with the arrangement of Fig. 1. It will be seen that bymoving aperture 5| across fluorescent screen 25, radiated energy fromany of the direction-indicating spots on fluorescent screen 25 may becaused to energize photocell 49. The signal output of the cell 49 isamplied in amplifier 52, differentiated in differentiating circuit 53,and utilized to overcome the normal cutoff bias on the sampling circuits35 and 41 so that the sampling circuits individually7 develop electricalsignals representative of the coordinates in the line-scanning andfield-scanning directions for the particular signal which is at themoment supplying energy to the photocell 49. Thus, it may be seen thatthe unit 48 is effective to supply to the sampling circuits 35 and 41only that portion of the time-modulated signal which corresponds to theparticular airplane whose coordinates of direction it is desired toindicate by Way of electrical signals. The di'erentiating circuit 53 isprovided so that the sampling circuits are responsive only to relativelyrapid changes in the signal input to the photocell 49. Such a rapidchange in the signal input to photocell 49 will be developed each timethe scanning beam of tube 24 becomes incident upon the particular spoton the iluorescent screen 25 which is being utilized to supply energy tothe photocell 49.

The arrangement of Fig. 4 is directed to a system for determining thescanning coordinates of the position of an object within a predeterminedspace in accordance with the present invention and is generally similarto the arrangement of Fig. 1, differing therefrom in that a camera tubeand signal generator 6E) are employed for deriving the time-modulatedsignal in place of the units Iii, il, 32 and 2| of the arrangement ofFig. l. Corresponding elements of the two systems bear identicalreference numerals and it will be understood that the units individuallyoperate in substantially the manner already described. The camera tubeand cathode-ray signal-generating device 60 is of a conventional designand may, for example, be similar to the signal-generating devicerepresented in Fig. l of United States Letters Patent 2,254,435, grantedSeptember 2, 1941 to Arthur V. Loughren, and assigned to the saineassignee as the present application. This unit includes asignal-generating tube having the usual electron gun, photosensitivetarget, and scanning elements. Beam-deecting voltages are applied to thedeflecting elements from line-scanning generator I3 and field-scanninggenerator l5 to deect the beam of the cathode-ray tube in two directionsnormal to each other to scan the photosensitive target in conventionalmanner.

In considering the operation of the arrangement of Fig. 4, it will beassumed that an image of the space including the object whosecoordinates it is desired to determine is focused upon the target of thecathode-ray signal-generating tube and that the electron beam of thetube is caused to scan the target in a series of fields of parallellines, thereby effectively to scan the space including the object and toderive the time-modulated signal representing the scanning coordinatesof the position of the object within space. This time-modulated signalin turn is applied to the brilliancy-control electrode 3D of thereproducing device 24 and to the control electrodes of the vacuum tubesincluded in the line-scanning sampling circuit 35 and field-scanningsampling circuit 41 whereby there is produced, in a manner fullydescribed above, a visual indication `onl area 25 of the coordinates ofthe object as well as electrical signals which represent the scanningcoordinates of the object. It will be understood that in thismodification of the invention there is a negligible time delay betweenthe scanning operation at the signal generator 6U and the correspondingscanning operation in the reproducing device 24. Consequently, thecompensating means provided in the arrangement of Fig. 1 is notnecessary in the arrangement under consideration.

In generating video-frequency signals by means of a cathode-ray typesignal-generating tube, undesirable transients are produced at the endof the line-trace period and during the line-retrace period. It isconventional to provide a blanking pulse generator which introduces intothe generated video-frequency signal blanking pulses extending in theblack direction to compensate the undesired transients so developed.While it is preferred that unit 50 include such a blanking pulsegenerator, means should also be included for reversing the polarity ofthe generated videofrequency signal before the application thereto ofthe blanking pulse. It will be understood that a video-frequency signalcorresponding to an airplane in a light sky comprises a substantiallywhite signal having a single pulse extending to the black level whichrepresents the airplane. If the blanking pulses are added to such asignal, the sampling circuits 35 and 41 would respond to the blankingsignals and provide an erroneous indi- 1593 cation of a coordinate. Toeliminate this source of error, it is proposed that the generatedvideofrequency signal be reversed in polarity so that it effectivelycomprises a substantially black signal having a single White pulserepresenting the position of the airplane in space. When the blankingpulses are superimposed on such a signal, only the white pulserepresenting the coordinate positions of the object is eiective tocontrol the sampling circuits.

From the foregoing description of the arrangement of Figs. 1 and 4, itwill be seen that the term object as employedA in the specication andclaims of this application refers to a physical device or an image ofthe device. It Will be understood, particularly in view of thediscussion of Fig. 3, that this invention may also be used to determinethe coordinates of a light spot on the screen of a cathode-ray tube and,accordingly, the term object also embraces a light spot.

It will be further understood that While the invention has beendescribed in connection with systems employing rectilinear scanning, theinvention is not limited thereto but is equally applicable to othertypes of scanning systems.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modilications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover al1 such changes and modificationsas fall Within the true spirit and scope of the invention.

What is claimed is:

1. A system for determining the scanning coordinate in a given scanningdirection of the position of an object Within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordinate in said scanning direction of the position of said objectWithin said space, means for deriving an electrical signal whichrepresents any selected scanning coordinate of said space in saidscanning direction, and means responsive to said first-named signal forcontrolling said last-mentioned means to derive an electrical signalwhich represents the scanning coordinate in said scanning direction ofthe position of said object Within said space.

2. A system for determining the scanning coordinate in a given scanningdirection of the position of an object Within a scanned spacecomprising, a radiating system including means for radiating a sharplyconcentrated beam and for causing said beam to scan said space in apredetermined scanning pattern, means for deriving from said beam asignal representing the scanning coordinate in said scanning directionof the position of said object Within said space, means for deriving anelectrical signal which represents any selected scanning coordinate ofsaid space in said scanning direction, and means responsive to saidfirst-named signal for controlling said last-mentioned means to derivean electrical signal which represents the scanning coordinate in saidscanning direction of the position of said object Within said space.

3. A system for determining the scanning coordinate in a given scanningdirection of the position of an object Within a scanned spacecomprising, a radiating system including means for radiating a sharplyconcentrated beam and for causing said beam to scan said space in .apredetermined scanning pattern, means for deriving a signal from energyof said beam reected from said object and representing the scanningcoordinate in said scanning direction of the position of said objectwithin said space, means for deriving an electrical signal whichrepresents any selected scanning coordinate of said space in saidscanning direction, and means responsive Y,

to said rst-named signal for controlling said last-mentioned means toderive an electrical'` sigprising, a radiating system including meansfor Y radiating a sharply concentrated beam and forcausing said beam toscan said spacein'a predetermined scanning pattern, means for deriving asignal from. energy from said beam` reflected from said object andrepresenting the scanning coordinate in said scanning direction of theposition of said object within said space, means for deriving anelectrical signal which represents any-selected scanning coordinate ofsaid space in said-scanning direction, means responsive to saidfirst-named signal for controlling said last-mentioned means to derivean electrical signal which represents Vlthe scanning coordinate in saidscanning direction of the position of said object Within said space, andmeans for compensating said first-named signal for the time required forsaid energy of said beam to travel from said radiating system to saidobject and` to said means for deriving said first-named signal. f

Y5.A system for determining the scanning coordinate in a given scanningdirection of the position of an object Withinv a scanned spacecomprising, a cathode-ray type signal generator including a target uponwhich an image of said space'is focused, means for producing an electronbeam and for causing'said beam to scan said image in a predeterminedscanning pattern to derive a signal representing the scanning coordinatein said scanning direction of the position of the image of said objectwithin said y, y

scanned image, means for deriving an electrical signal which representsany selected scanning coordinate of said scanned image in said scanningdirection, and means responsive to said iirstnamed signal forcontrolling said last-mentioned means to derive an electrical signalwhich represents the scanning coordinate in said scanning di- V rectionof the position of the image of said object Within said scanned image.

6. A system for determining the scanning coordinatein a given scanningdirection of the position of an object Within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordinate in said scanning direction of the position of said objectWithin said space, means for deriving a reference Wave havinginstantaneous amplitude values related to the scanning coordinates insaid scanning direction of said space, means responsive to saidreference wave for deriving an electrical signal which represents 'anyselected scanning coordinate of said space in said scanning direction,and means responsive to said rst-named signal for controlling saidlast-mentioned means to derive an electrical signal which represents thescanning coordinate in said scan- 1I ning direction of the position ofsaid object within said space.

7. A system for determining the scanning coordinate in a given scanningdirection of the position of an object within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordiate in said scanning direction of the position of said objectWithin said space, means for deriving a reference Wave havinginstantaneous amplitude values related to the scanning coordinates insaid scanning direction of said space, means responsive to an amplitudecharacteristic of said reference Wave for deriving an electrical signalwhich represents any selected scanning coordinate of said space in saidscanning direction, and means responsive to said first-named signal forcontrolling said last-mentioned means to derive an elecm trical signalwhich represents the scanning coordinate in said scanning direction ofthe position of said object Within said space.

8. A system for determining the scanning coordinate in a given scanningdirection of the posi tion of an object within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordiate in said scanning direction of the position of said objectWithin said scanned space, means for deriving a reference Wave havinginstantaneous amplitude values related to the scanning coordinates insaid scanning direction of said space, means responsive to saidreference wave for deriving an electrical signal which represents anyselected scanning coordinate of said space in said scanning directionand including a vacuum tube having a control electrode, and means forapplying said rst-named signal to said control electrode for controllingsaid last-mentioned means to derive an electrical signal whichrepresents the scanning .coordinate in said scanning direction of theposition of said oloject Within said space.

9. A system for determining the scanning coordinate in a given scanningdirection of the position of an object Within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordiate in said scanning direction of the position of said objectWithin said space, a generator for controlling the scanning component ofsaid scanning means in said scanning direction, means coupled to saidgenerator for deriving an electrical signal which represents anyselected scanning coordinate of said space in said scanning direction,and means responsive to said rst-named signal for controlling saidlast-mentioned means to derive an electrical signal which represents thescanning coordinate in said scanning direction of the position of saidobject Within said space.

10. A system for determining the scanning cordinate in a given scanningdirection of the position of an object within a scanned spacecomprising, means for eectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordinate in said scanning direction of the position of said objectwithin said space, means for deriving a reference Wave havinginstantaneous amplitude values corresponding to the scanning componentof said scanning pattern in said scanning direction, and meansresponsive to the relative phase of said reference Wave and saidfirst-named signal for deriving an electrical signal which representsthe scanning coordinate in said scanning direction of the position ofsaid object within said space.

11. A system for determining the scanning coordinate in a given scanningdirection of the position of an object Within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordinate in said scanning direction of the position of said objectWithin said space, signal-reproducing means responsive to said signalfor producing a visual indication of the scanning coordinate in saidscanning direction of the position of said object Within said space,means for deriving an electrical signal which represents any selectedscanning coordinate of said space in said scanning direction, and meansresponsive to said firstnamed signal for con-trolling saidlast-mentioned means to derive an electrical signal which represents thescanning coordinate in said scanning direction of the position of saidobject within said space.

l2. A system for determining the scanning coordinate in a given scanningdirection of the position of an object within a scanned spacecomprising, means for effectively scanning said space in a predeterminedscanning pattern and for deriving a signal representing the scanningcoordinate in said scanning direction of the position of said objectwithin said space, a cathode-ray type signal-reproducing deviceincluding an indicating area, means for scanning said indicating area insynchronism with the scanning of said space, means responsive to saidsignal for producing on said indicating area a visual indication of thescanning coordinate in said scanning direction of the position of saidobject Within said space, means for deriving an electrical signal whichrepresents any selected scanning coordinate of said space in saidscanning direction, and means responsive to said rst-named signal forcontrolling said last-mentioned means to derive an electrical signalwhich represents the scanning coordinate in said scanning direction ofthe position of said object within said space.

13. A system for determining the scanning coordinate in a given scanningdirection of the position of a particular one of a plurality of objectswithin a scanned space comprising, means for effectively scanning saidspace in a predetermined scanning pattern and for deriving a signalrepresenting the scanning coordinate in said scanning direction of theposition of each of said objects Within said space, means for derivingan electrical signal which represents any selected scanning coordinateof said space in said scanning direction, and means responsive to aselected portion of said first-named signal for controlling saidlast-mentioned means to derive an electrical signal which represents thescanning coordinate in said scanning direction of the position of saidparticular object Within said space.

ARTHUR V. LOUGI-IREN.

